On the other hand, the largest negative impact on the simulation will be the PS1 camera fill-factor. The effective camera fill-factor (f) is reduced by the metal lines between individual OTA cells, the gaps between the CCDs, the use of some cells for guide star acquisition, dead cells, bad cells (e.g. due to charge transfer efficiency problems or dark noise) and the removal of portions of the image by the PS1 funding agency to excise fast moving satellites. We expect the overall fill-factor due to all these effects to result in f 0.88. As described above, for Solar System discoveries we require six etections on three nights within a lunation. Thus, the impact of the fill-factor on the detection efficiency () for fast moving objects like the impactor population is simply = f 6 0.46 if the inactive area is uncorrelated on the focal plane or = f 3 0.68 if it is correlated. That is, if the first detection of an object appears on an inactive area then its second detection is also likely to appear on an inactive area in the ‘correlated’ case and unlikely to do so in the ‘uncorrelated’ case. Losing 13 to 12
of potential discoveries due to the fill-factor is unfortunate but the loss is mitigated for slow moving distant objects ecause they appear near opposition in successive lunations. PS1 has two opportunities to discover the object in each of two successive lunations so the efficiency for finding these objects will be J90%. The problem is worse for objects like NEOs and impactors that spend fewer lunations above the detection threshold.